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Red Hat Enterprise Linux 50
Red Hat Enterprise Linux
bull Enterprise-targeted operating systembull Focused on mature open source technologybull 18-24 month release cycle Certified with leading OEM and ISV productsbull Two variants available Server Clientbull Purchased with one year Red Hat Network subscription
and support contract Support available for seven years after release Up to 24x7 coverage plans available
Other Red Hat Supported Software
bull Global File system
bull Directory Server
bull Certificate Server
bull Red Hat Application Stack
bull JBoss Middleware Application Suite
Notes on Internationalization
bull Red Hat Enterprise Linux supports nineteen languages
bull Default language can be selected During installation With system-config-languagebull System-gtAdministration-gtLanguagebull Alternate languages can be used on a per-
command basis $ LANG=en_USUTF8 date Language settings are stored in
etcsysconfigi18n
The Fedora Project
bull Red Hat sponsored open source projectbull Focused on latest open source technology Rapid four to six month release cycle Available as free download from the
Internetbull An open community-supported proving
ground for technologies which may be used in upcoming enterprise products
bull Red Hat does not provide formal support
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Red Hat Enterprise Linux
bull Enterprise-targeted operating systembull Focused on mature open source technologybull 18-24 month release cycle Certified with leading OEM and ISV productsbull Two variants available Server Clientbull Purchased with one year Red Hat Network subscription
and support contract Support available for seven years after release Up to 24x7 coverage plans available
Other Red Hat Supported Software
bull Global File system
bull Directory Server
bull Certificate Server
bull Red Hat Application Stack
bull JBoss Middleware Application Suite
Notes on Internationalization
bull Red Hat Enterprise Linux supports nineteen languages
bull Default language can be selected During installation With system-config-languagebull System-gtAdministration-gtLanguagebull Alternate languages can be used on a per-
command basis $ LANG=en_USUTF8 date Language settings are stored in
etcsysconfigi18n
The Fedora Project
bull Red Hat sponsored open source projectbull Focused on latest open source technology Rapid four to six month release cycle Available as free download from the
Internetbull An open community-supported proving
ground for technologies which may be used in upcoming enterprise products
bull Red Hat does not provide formal support
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Other Red Hat Supported Software
bull Global File system
bull Directory Server
bull Certificate Server
bull Red Hat Application Stack
bull JBoss Middleware Application Suite
Notes on Internationalization
bull Red Hat Enterprise Linux supports nineteen languages
bull Default language can be selected During installation With system-config-languagebull System-gtAdministration-gtLanguagebull Alternate languages can be used on a per-
command basis $ LANG=en_USUTF8 date Language settings are stored in
etcsysconfigi18n
The Fedora Project
bull Red Hat sponsored open source projectbull Focused on latest open source technology Rapid four to six month release cycle Available as free download from the
Internetbull An open community-supported proving
ground for technologies which may be used in upcoming enterprise products
bull Red Hat does not provide formal support
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Notes on Internationalization
bull Red Hat Enterprise Linux supports nineteen languages
bull Default language can be selected During installation With system-config-languagebull System-gtAdministration-gtLanguagebull Alternate languages can be used on a per-
command basis $ LANG=en_USUTF8 date Language settings are stored in
etcsysconfigi18n
The Fedora Project
bull Red Hat sponsored open source projectbull Focused on latest open source technology Rapid four to six month release cycle Available as free download from the
Internetbull An open community-supported proving
ground for technologies which may be used in upcoming enterprise products
bull Red Hat does not provide formal support
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The Fedora Project
bull Red Hat sponsored open source projectbull Focused on latest open source technology Rapid four to six month release cycle Available as free download from the
Internetbull An open community-supported proving
ground for technologies which may be used in upcoming enterprise products
bull Red Hat does not provide formal support
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Objectives
bull A user who can use effectively employ RedHat Enterprise Linux to customize his or heroperating environment as well as accomplishcommon command-line tasks and desktop productivity roles
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Audience and Prerequisites
bull Audience Users new to Linux and UNIX users and administrators transitioning from another operating system
bull User-level experience with any computer system use of mouse menus and any graphical user interface
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 1
Linux Ideas and History
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
What is Open Source
bull Open source software and source code available to all
The freedom to distribute software and source code
The ability to modify and create derived works
Integrity of authors codebull The Free Software Foundation and the Four
Freedoms
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Linux Origins
bull 1984 The GNU Project and the Free Software Foundation Creates open source version of UNIX utilities Creates the General Public License (GPL) Software license enforcing open source principlesbull 1991 Linus Torvaldsbull Creates open source UNIX-like kernel released under the
GPL Ports some GNU utilities solicits assistance onlinebull Today Linux kernel + GNU utilities = complete open source UNIX-like operating system Packaged for targeted audiences as distributions
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Red Hat Distributions
bull Linux distribution are OSes based on the Linux kernelbull Red Hat Enterprise Linux
Stable thoroughly tested softwareProfessional support servicesCentralized management tools for large networks
bull The Fedora ProjectMore newer applicationsCommunity supported (no official Red Hat
support)For personal systems
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Linux principles
bull Everything is a file (including hardware)bull Small single-purpose programsbull Ability to chain programs together to
perform complex tasksbull Avoid captive user interfacesbull Configuration data stored in text
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 2
Linux Usage Basics
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Logging in to a Linux System
bull Two types of login screens virtual consoles
(text-based) and graphical logins (called display
managers)bull Login using login name and passwordbull Each user has a home directory for personal
file storage
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Switching between virtual consolesand the graphical environment
bull A typical Linux system will run six virtual
consoles and one graphical console
Server systems often have only virtual consoles
Desktops and workstations typically have both
bull Switch among virtual consoles by typing
Ctrl-Alt-F[1-6]
bull Access the graphical console by typing Ctrl-Alt-F7
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Elements of the X Window System
bull The X Window System is Linuxs graphical subsystem
bull Xorg is the particular version of the X Window System used by Red Hat
Open source implementation of Xbull Look and behavior largely controlled by the desktop
environmentbull Two desktop environments provided by Red Hat GNOME the default desktop environment KDE an alternate desktop environment
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Starting the X server
bull On some systems the X server starts automatically at boot time
bull Otherwise if systems come up in virtual consoles users must start the X server manually
bull The X server must be pre-configured by the systembull administratorbull 1048576m Log into a virtual console and run startxbull 1048576m The X server appears on Ctrl-Alt-F7
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing Your Password
bull Passwords control access to the system Change the password the first time you log in Change it regularly thereafter Select a password that is hard to guessbull To change your password using GNOME navigate to System-gtPreferences-gtAbout Me and then click Passwordbull To change your password from a terminalpasswd
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The root user
bull The root user a special administrative accountAlso called the superuser root has near complete control over the systemand a nearly unlimited capacity to damage itbull Do not login as root unless necessaryNormal(unprivileged ) userspotential to do damage is more limited
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing Identities
bull su - creates new shell as root
bull sudo command runs command as root
Requires prior configuration by a system administrator
bull id shows information on the current user
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Editing text files
bull The nano editor Easy to learn easy to use Not as feature-packed as some advanced
editorsbull Other editors gedit a simple graphical editor vim an advanced full feature editor gvim a graphical version of the vim editor
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 3
Running Commands andGetting Help
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Running Commands
bull Commands have the following syntax command options arguments
bull Each item is separated by a spacebull Options modify a commands behavior Single-letter options usually preceded by - Can be passed as -a -b -c or -abc Full-word options usually preceded by -- Example --helpbull Arguments are filenames or other data needed
by the commandbull Multiple commands can be separated by
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Some Simple Commands
bull date - display date and time
bull cal - display calendar
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Getting Help
bull Dont try to memorize everything
bull Many levels of help
whatis
command --help
man and info
usrsharedoc
Red Hat documentation
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The whatis Command
bull Displays short descriptions of commands
bull Uses a database that is updated nightly
bull Often not available immediately after install
$ whatis cal
cal (1) - displays a calendar
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The --help Option
bull Displays usage summary and argument listbull Used by most but not all commands $ date --help Usage date [OPTION] [+FORMAT] or date [-u|--utc|--universal] [MMDDhhmm[[CC]YY]
[ss]] Display the current time in the given FORMAT or set the system date argument list omitted
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The man Command
bull Provides documentation for commands
bull Almost every command has a man page
bull Pages are grouped into chapters
bull Collectively referred to as the Linux Manual
bull man [ltchaptergt] ltcommandgt
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Navigating man Pages
bull While viewing a man page Navigate with arrows PgUp PgDn text searches for text nN goes to nextprevious match q quitsbull Searching the Manual man -k keyword lists all matching pages Uses whatis database
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The info Command
bull Similar to man but often more in-depth
bull Run info without args to list all page
bull info pages are structured like a web site
Each page is divided into nodes
Links to nodes are preceded by
info [command]
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Navigating info Pages
bull While viewing an info page Navigate with arrows PgUp PgDn Tab moves to next link Enter follows the selected link np u goes to the nextpreviousup-one node s text searches for text (default last search) q quits info
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Extended Documentation
bull The usrsharedoc directory
Subdirectories for most installed packages
Location of docs that do not fit elsewhere
Example configuration files
HTMLPDFPS documentation
License details
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Red Hat Documentation
bull Available on docs CD or Red Hat website
Installation Guide
Deployment Guide
Virtualization Guide
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 4
Browsing the Filesystem
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Linux File Hierarchy Concepts
bull Files and directories are organized into a
single-rooted inverted tree structure
bull Filesystem begins at the root directory represented by a lone (forward slash) character
bull Names are case-sensitive
bull Paths are delimited by
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Some Important Directories
bull Home Directories roothomeusernamebull User Executables bin usrbin usrlocalbinbull System Executables sbin usrsbin
usrlocalsbinbull Other Mountpoints media mntbull Configuration etcbull Temporary Files tmpbull Kernels and Bootloader bootbull Server Data var srvbull System Information proc sysbull Shared Libraries lib usrlib usrlocallib
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Current Working Directory
bull Each shell and system process has a current working directory (cwd)
bull pwd Displays the absolute path to the shells
cwd
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
File and Directory Names
bull Names may be up to 255 charactersbull All characters are valid except the forward slash
It may be unwise to use certain special characters in file or directory names
Some characters should be protected with quotes when referencing them
bull Names are case-sensitive
Example MAIL Mail mail and mAiL
Again possible but may not be wise
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Absolute and Relative Pahnames
bull Absolute pathnames Begin with a forward slash Complete road map to file location Can be used anytime you wish to specify a file namebull Relative pathnames Do not begin with a slash Specify location relative to your current working
directory Can be used as a shorter way to specify a file name
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing Directories
bull cd changes directories To an absolute or relative path cd homejoshuawork cd projectdocs To a directory one level up cd To your home directory cd To your previous working directory cd -
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Listing Directory Contents
bull Lists the contents of the current directory or a specified directory
bull Usage
ls [options] [files_or_dirs]bull Example
ls -a (include hidden files)
ls -l (display extra information)
ls -R (recurse through directories)
ls -ld (directory and symlink information)
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Copying Files and Directories
bull cp - copy files and directoriesbull Usage cp [options] file destinationbull More than one file may be copied at a time
if the destination is a directory cp [options] file1 file2 dest
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Copying Files and Directories The Destination
bull If the destination is a directory the copy is placed there
bull If the destination is a file the copy overwrites the destination
bull If the destination does not exist the copy is renamed
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Moving and Renaming Files andDirectories
bull mv - move andor rename files and directoriesbull Usage
mv [options] file destinationbull More than one file may be moved at a time if the
destination is a directory
mv [options] file1 file2 destinationbull Destination works like cp
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Creating and Removing Files
bull touch - create empty files or update file timestamps
bull rm - remove filesbull Usage
rm [options] ltfilegtbull Example
rm -i file (interactive)
rm -r directory (recursive)
rm -f file (force)
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Creating and Removing Directories
bull mkdir creates directories
bull rmdir removes empty directories
bull rm -r recursively removes directory trees
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Using Nautilus
bull Gnome graphical filesystem browserbull run in browser modebull Accessed via
Desktop icons
Home Your home directory
Computer Root filesystem network resources
and removable media
Applications-gtSystem Tools-gtFile Browser
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Moving and Copying in Nautilus
bull Drag-and-Drop
Drag Move on same filesystem copy on different filesystem
Drag + Ctrl Always copy
Drag + Alt Ask whether to copy move or create symbolic link (alias)
bull Context menu
Right-click to rename cut copy or paste
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Determining File Content
bull Files can contain many types of databull Check file type with file before opening to
determine appropriate command or application to use
bull file [options] ltfilenamegt
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 5
Users Groups and Permissions
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Users
bull Every user is assigned a unique User ID number (UID ) UID 0 identifies rootbull Users names and UIDs are stored in etc
passwdbull Users are assigned a home directory and a program that is run when they log in (usually a shell)bull Users cannot read write or execute each others files without permission
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Groups
bull Users are assigned to groupsbull Each group is assigned a unique Group ID number (gid )bull GIDs are stored in etcgroupbull Each user is given their own private group Can be added to other groups for additional
accessbull All users in a group can share files that belong to the group
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Linux File Security
bull Every file is owned by a UID and a GIDbull Every process runs as a UID and one or more
GIDs Usually determined by who runs the processbull Three access categories Processes running with the same UID as the
file (user ) Processes running with the same GID as the
file (group ) All other processes (other )
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Permission Precedence
bull If UID matches user permissions apply
bull Otherwise if GID matches group permissions apply
bull If neither match other permissions apply
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Permission Types
bull Four symbols are used when displaying permissions
r permission to read a file or list a directorys contents w permission to write to a file or create and
remove files from a directory x permission to execute a program or change
into a directory and do a long listing of the directory
- no permission (in place of the r w or x)
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Examining Permissions
bull File permissions may be viewed using ls -l
$ ls -l binlogin
-rwxr-xr-x 1 root root 19080 Apr 1 1826 binlogin
bull File type and permissions represented by a 10-character string
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Interpreting Permissions
-rwxr-x--- 1 andersen trusted 2948 Oct 11 1407 myscript
bull Read Write and Execute for the owner andersen
bull Read and Execute for members of the trusted group
bull No access for all others
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing File Ownership
bull Only root can change a files ownerbull Only root or the owner can change a files groupbull Ownership is changed with chown
chown [-R] user_name file|directorybull Group-Ownership is changed with chgrp
chgrp [-R] group_name file|directory
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing Permissions - SymbolicMethod
bull To change access modes
chmod [-R] mode filebull Where mode is
ug or o for user group and other
+ or - for grant or deny
r w or x for read write and executebull Examples
ugo+r Grant read access to all
o-wx Deny write and execute to others
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Changing Permissions - NumericMethod
bull Uses a three-digit mode number first digit specifies owners permissions
second digit specifies group permissions third digit represents others permissionsbull Permissions are calculated by adding 4 (for read) 2 (for write) 1 (for execute)bull Example chmod 640 myfile
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 6
Using the bash Shell
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Command Line ShortcutsThe Tab Key
bull Type Tab to complete command lines For the command name it will complete a
command name For an argument it will complete a file namebull Examples $ xteltTabgt $ xterm $ ls myfltTabgt $ ls myfiletxt
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Command Line ShortcutsHistory
bull bash stores a history of commands youveentered which can be used to repeat commandsbull Use history command to see list of
remembered commands $ history 14 cd tmp 15 ls -l 16 cd 17 cp etcpasswd 18 vi passwd output truncated
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
More History Tricks
bull Use the up and down keys to scroll through
previous commandsbull Type Ctrl-r to search for a command in
command history
(reverse-isearch)`
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Command Line ExpansionThe tilde
bull Tilde ( ~ )bull May refer to your home directory$ cat ~bash_profilebull May refer to another users home directory$ ls ~juliepublic_html
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Command Line ExpansionCommands and Braced Sets
bull Command Expansion $() or `` Prints output of one command as an argument to another $ echo This systems name is $(hostname) This systems name is server1examplecombull Brace Expansion Shorthand for printing repetitive strings $ echo file135 file1 file3 file5 $ rm -f file135
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Command Editing Tricks
bull Ctrl-a moves to beginning of line
bull Ctrl-e moves to end of line
bull Ctrl-u deletes to beginning of line
bull Ctrl-k deletes to end of line
bull Ctrl-arrow moves left or right by word
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
gnome-terminal
bull Applications-gtAccessories-gtTerminal
bull Graphical terminal emulator that supports
bull multiple tabbed shells
Ctrl-Shift-t creates a new tab
Ctrl-PgUpPgDn switches to nextprev tab
Ctrl-Shift-c copies selected text
Ctrl-Shift-v pastes text to the prompt
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Scripting Basics
bull Shell scripts are text files that contain a series of commands or statements to be executed
bull Shell scripts are useful for Automating commonly used commands Performing system administration and troubleshooting Creating simple applications Manipulation of text or files
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Creating Shell Scripts
bull Step 1 Use such as vi to create a text file containing commands
First line contains the magic
shebang sequence
binbashbull Comment your scripts
Comments start with a
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Creating Shell Scriptscontinued
bull Step 2 Make the script executable $ chmod u+x myscriptshbull To execute the new script Place the script file in a directory in the executable path -OR- Specify the absolute or relative path to the script on the command line
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Sample Shell Script
bull binbashbull This script displays some information about
your environment
echo Greetings The date and time are $(date)
echo Your working directory is $(pwd)
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 7
vim An Advanced Text Editor
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Introducing vim
bull Newer version of vi the standard Unix text editor Executing vi runs vim by defaultbull gvim Graphical version of vim Applications + Programming -gt Vi iMproved Provided by vim-X11 packagebull Advantages Speed Do more with fewer keystrokes Simplicity No dependence on mouseGUI Availability Included with most Unix-like OSesbull Disadvantages Difficulty Steeper learning curve than simpler editors Key bindings emphasize speed over intuitiveness
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
vim A Modal Editor
bull Keystroke behavior is dependent upon vims modebull Three main modes Command Mode (default) Move cursor cutpaste text change mode Insert Mode Modify text Ex Mode Save quit etcbull Esc exits current modebull EscEsc always returns to command mode
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
vim Basics
bull To use vim you must at least be able to
Open a file
Modify a file (insert mode)
Save a file (ex mode)
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Opening a file in vim
bull To start vi
vim filename
If the file exists the file is opened and the contents are displayed
If the file does not exist vi creates it when the edits are saved for the first time
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Modifying a FileInsert Mode
bull i begins insert mode at the cursorbull Many other options exist
A append to end of line
I insert at beginning of line
o insert new a line (below)
O insert new line (above)
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Saving a File and Exiting vimEx Mode
bull Enter Ex Mode with Creates a command prompt at bottom-left of
screenbull Common writequit commands w writes (saves) the file to disk wq writes and quits q quits even if changes are lost
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Using Command Mode
bull Default mode of vimbull Keys describe movement and text manipulation
commandsbull Commands repeat when preceded by a numberbull Example Right Arrow moves right one character 5 Right Arrow moves right five characters
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Moving AroundCommand Mode
bull Move by character Arrow Keys h j k l Non-arrow keys useful for remote connections to older
systemsbull Move by word w bbull Move by sentence ) (bull Move by paragraph bull Jump to line x xGbull Jump to end G
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Undoing ChangesCommand Mode
bull u undo most recent change
bull U undo all changes to the current line since the cursor landed on the line
bull Ctrl-r redo last undone change
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Learning more
bull vivim built-in help
help
help topic
Use q to exit helpbull vimtutor command
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 8
Basic System ConfigurationTools
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
TCPIP Network Configuration
bull Important network settings
IP Configuration
Device Activation
DNS Configuration
Default Gateway
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Managing Ethernet Connections
bull Network interfaces are named sequentially eth0 eth1 etc Multiple addresses can be assigned to a device
with aliases Aliases are labeled eth01 eth02 etc Aliases are treated like separate interfacesbull View interface configuration with ifconfig [ethX] Enable interface with ifup ethX Disable interface with ifdown ethX
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Graphical Network Configurationsystem-config-network
bull System-gtAdministration-gtNetwork
ActivateDeactivate interfaces
Assign IP AddressesDHCP
Modify DNS settings
Modify gateway address
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Network Configuration FilesEthernet Devices
bull Device configuration is stored in text files etcsysconfignetwork-scriptsifcfg-ethX
bull Complete list of options in usrsharedocinitscripts-sysconfigtxt
Dynamic Configuration Static Configuration
DEVICE=ethX DEVICE=ethX HWADDR=0028AA63045 HWADDR=0028AA63045 BOOTPROTO=dhcp IPADDR=1921680254 ONBOOT=yes NETMASK=2552552550 Type=Ethernet GATEWAY=1921682254 ONBOOT=yes Type=Ethernet
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Network Configuration FilesOther Global Network Settings
bull Global Settings in etcsysconfig network Many may be provided by DHCP GATEWAY can be overridden in ifcfg file NETWORKING=yes HOSTNAME=server1examplecom GATEWAY=1921682254
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Network Configuration FilesDNS Configuration
bull Domain Name Service translates hostnames to network addresses
bull Server address is specified by dhcp or in etcresolvconf
search examplecom crackerorg nameserver 1921680254 nameserver 1921681254
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Printing in Linux
bull Printers may be local or networked
bull Print requests are sent to queues
bull Queued jobs are sent to the printer on a first come first served basis
bull Jobs may be canceled before or during printing
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
system-config-printer
bull System-gtAdministration-gtPrintingbull Supported printer connections
Local (parallel or usb)
UnixLinux print server
Windows print server
Netware print server
HP JetDirectbull Configuration stored in etccupsprintersconf
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Printing Commands
bull lpr sends a job to the queue to be printed
Accepts ASCII PostScript PDF othersbull lpq views the contents of the queuebull lprm removes a job from the queuebull System V printing commands such as lpbull lpstat and cancel are also supported
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Setting the Systems Date and Time
bull GUI system-config-date System-gtAdministration-gtDate amp Time Can set datetime manually or use NTP Additional NTP servers can be added Can use local time or UTCbull CLI date [MMDDhhmm[[CC]YY][ss]] date 01011330 date 01011330200705
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 9Investigating and ManagingProcesses
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
What is a Process
bull A process is a set of instructions loaded into memory
Numeric Process ID (PID) used for identificationbull UID GID and SELinux context determines
filesystem access Normally inherited from the executing user
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Listing Processes
bull View Process information with ps Shows processes from the current terminal bybull default -a includes processes on all terminals -x includes processes not attached to terminals -u prints process owner information -f prints process parentage -o PROPERTY prints custom information pid comm cpu mem state tty euser ruser
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Finding Processes
bull Most flexible ps options | otherbull commands ps axo commtty | grep ttyS0bull By predefined patterns pgrep $ pgrep -U root $ pgrep -G studentbull By exact program name pidof $ pidof bash
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Signals
bull Most fundamental inter-process communication Sent directly to processes no user-interface
required Programs associate actions with each signal Signals are specified by name or number when
sent Signal 15 TERM (default) - Terminate cleanly Signal 9 KILL - Terminate immediately Signal 1 HUP - Re-read configuration files man 7 signal shows complete list
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Sending Signals to Processes
bull By PID kill [signal] pid bull By Name killall [signal] comm bull By pattern pkill [-signal] pattern
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Scheduling Priority
bull Scheduling priority determines access to the CPU
bull Priority is affected by a process nice valuebull Values range from -20 to 19 but default to
0bull Lower nice value means higher CPU
prioritybull Viewed with ps -o commnice
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Altering Scheduling Priority
bull Nice values may be altered
When starting a process
$ nice -n 5 command
After starting
$ renice 5 PIDbull Only root may decrease nice values
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Interactive Process Management Tools
bull CLI topbull GUI gnome-system-monitorbull Capabilities
Display real-time process information
Allow sorting killing and re-nicing
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Job Control
bull Run a process in the background Append an ampersand to the command line
firefox ampbull Temporarily halt a running program Use Ctrl-z or send signal 17 (STOP)bull Manage background or suspended jobs List job numbers and names jobs Resume in the background bg [jobnum] Resume in the foreground fg [jobnum] Send a signal kill [-SIGNAL] [jobnum]
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Grouping Commands
bull Two ways to group commands
Compound date who | wc -lbull Commands run back-to-back
Subshell (date who | wc -l) gtgt tmptrace
All output is sent to a single STDOUT and STDERR
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Exit Status
bull Processes report success or failure with an
exit status
0 for success 1-255 for failure
$ stores the exit status of the most recent
commandbull Example
$ ping -c1 -W1 station999 ampgt devnull
$ echo $
2
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 10Configuring the Bash Shell
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Aliases
bull Aliases let you create shortcuts to commands
$ alias dir=ls -laF
bull Use alias by itself to see all set aliases
bull Use alias followed by an alias name to see alias value
$ alias dir
alias dir=ls -laF
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Login vs non-login shells
bull Startup is configured differently for login andnon-login shellsbull Login shells are Any shell created at login (includes X login) su -bull Non-login shells are su graphical terminals executed scripts any other bash instances`
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Bash startup tasks profile
bull Stored in etcprofile (global) and ~ bash_profile (user)bull Run for login shells only bull Used for Setting environment variables Running commands (eg mail-checker script)
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Bash startup tasks bashrc
bull Stored in etcbashrc (global) and ~bashrc (user)
bull Run for all shellsbull Used for Setting local variables Defining aliases
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Bash exit tasks
bull Stored in ~bash_logout (user)bull Run when a login shell exitsbull Used for
Creating automatic backups
Cleaning out temporary files
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 11Finding and Processing Files
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Objectives
Upon completion of this unit you should be
able tobull Use locatebull Use findbull Use the Gnome Search tool
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
locate
bull Queries a pre-built database of paths to files on the system
Database must be updated by administrator
Full path is searched not just filenamebull May only search directories where the user has
read and execute permission
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
locate Examples
bull locate foo Search for files with foo in the name or pathbull locate -r foo$bull Regex search for files ending in foobull Useful options -i performs a case-insensitive search -n X lists only the first X matches
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
find
bull find [directory] [criteria]bull Searches directory trees in real-time Slower but more accurate than locate CWD is used if no starting directory given All files are matched if no criteria givenbull Can execute commands on found filesbull May only search directories where the userhas read and execute permission
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Basic find Examples
bull find -name snowpngSearch for files named snowpngbull find -iname snowpngbull 1048576m Case-insensitive search for files named
snowpngbull Snowpng SNOWPNG etcbull find -user joe -group joebull 1048576m Search for files owned by the user joe andbull the group joe
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
find and Logical Operators
bull Criteria are ANDed together by defaultbull Can be ORd or negated with -o and -notbull Parentheses can be used to determine logic
order but must be escaped in bashndash find -user joe -not -group joendash find -user joe -o -user janendash find -not ( -user joe -o -user jane )
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
find and Permissions
bull Can match ownership by name or idndash find -user joe -o -uid 500
bull Can match octal or symbolic permissionsndash find -perm 755 matches if mode is
exactly 755ndash find -perm +222 matches if anyone can writendash find -perm -222 matches if everyone can writendash find -perm -002 matches if other can write
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
find and Numeric Criteria
bull Many find criteria take numeric valuesbull find -size 1024k Files with a size of exactly 1megabytebull find -size +1024k Files with a size over 1 megabytebull find -size -1024k Files with a size less than 1 megabyte
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
find and Access Times
bull find can match by inode timestamps -atime when file was last read -mtime when file data last changed -ctime when file data or metadata last
changedbull Value given is in days find -ctime -10 Files modified less than 10 days ago
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Executing Commands with find
bull Commands can be executed on found files
Command must be preceded with -exec or -ok
-ok prompts before acting on each file
Command must end with Space
Can use as a filename placeholder
find -size +102400k -ok gzip
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The Gnome Search Tool
bull Places-gtSearch for Filesbull Graphical tool for searching by
name
content
ownergroup
size
modification time
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 12Network Clients
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Web Clients
bull Firefoxbull Other web browsersbull Non-GUI web browsersbull wget
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Firefox
bull Fast lightweight feature-rich web browser
Tabbed browsing
Popup blocking
Cookie management
Multi-engine search bar
Support for many popular plug-insbull Themes and Extensions
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Non-GUI Web Browsers
bull links
Provided by the elinks rpm
Full support for frames and ssl
Examples
links httpwwwredhatcom
links -dump httpwwwredhatcom
links -source httpwwwredhatcom
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
wget
bull Retrieves files via HTTP and FTPbull Non-interactive - useful in shell scriptsbull Can follow links and traverse directory trees
on the remote server - useful for mirroring web
and FTP sites
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
OpenSSH Secure Remote Shell
bull Secure replacement for older remote-access tools
bull Allows authenticated encrypted access to
remote systems
ssh [user]hostname
ssh [user]hostname command
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
scp Secure File Transfer
bull Secure replacement for rcpbull Layered on top of ssh
ndash scp source destinationndash Remote files can be specified using
bull [user]hostpathtofile
ndash Use -r to enable recursionndash Use -p to preserve times and permissionsndash Use -C to compress datastream
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
rsync Efficient File Sync
bull Efficiently copies files to or from remote
bull systems
bull Uses secure ssh connections for transportndash rsync conf barneyhomejoeconfigs
bull Faster than scp - copies differences in like
files
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
FTP Clients
bull CLI lftp$ lftp ftpexamplecom$ lftp -u joe ftpexamplecom
ndash Automated transfers with lftpget
bull GUI gFTPndash Applications-gtInternet-gtgFTPndash Allows Drag-and-Drop transfersndash Anonymous or authenticated accessndash Optional secure transfer via ssh (sftp)
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Network Diagnostic Tools
ping
traceroute
host
dig
netstat
gnome-nettool (GUI)
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 15
Advanced Topics in Users
Groups and Permissions
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
User and Group ID Numbers
bull User names map to user ID numbers
bull Group names map to group ID numbers
bull Data stored on the hard disk is stored
numerically
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
etcpasswd etcshadow and etcgroup files
bull Authentication information is stored in plain text filesndash etcpasswdndash etcshadowndash etcgroupndash etcgshadow
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
User management tools
bull Graphical toolsndash system-config-users
bull Command-linendash useraddndash usermodndash userdel [-r]
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Monitoring Logins
bull Connected users w
bull Recent Logins last lastb
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Default Permissions
bull Default permission for directories is 777 minus umask
bull Default permission for files is the directory default without execute permissionndash umask is set with the umask commandndash Non-privileged users umask is 002
bull Files will have permissions of 664bull Directories will have permissions of 775
bull roots umask is 022
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Special Permissions for Executables
bull Special permissions for executablesndash suid command run with permissions of the owner of
the command not executor of the commandndash sgid command runs with group affiliation of the group
of the command
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Special Permissions for Directories
bull Special permissions for directoriesndash sticky bit files in directories with the sticky bit
set can only be removed by the owner and root regardless of the write permissions of the directory
ndash sgid files created in directories with the sgid bit set have group affiliations of the group of the directory
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Unit 16
The Linux Filesystem In-Depth
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Partitions and Filesystems
bull Disk drives are divided into partitionsbull Partitions are formatted with filesystems
allowing users to store datandash Default filesystem ext3 the Third Extended Linux
Filesystemndash Other common filesystemsndash ext2 and msdos (typically used for floppies)ndash iso9660 (typically used for CDs)ndash GFS and GFS2 (typically for SANs)
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Hard Links
bull A hard link adds an additional pathname to reference a single filendash One physical file on the filesystemndash Each directory references the same inode numberndash Increments the link count
bull The rm command decrements the link countbull File exists as long as at least one link remainsbull When the link count is zero the file is removed
ndash Cannot span drives or partitions
bull Syntaxndash ln filename [linkname]
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Symbolic (or Soft) Links
bull A symbolic link points to another filendash ls -l displays the link name and the referenced file
lrwxrwxrwx 1 joe joe 11 Sep 25 1802 pf -gtetcpasswdndash File type l for symbolic linkndash The content of a symbolic link is the name of the file
that it references
bull Syntaxndash ln -s filename linkname
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
The Seven Fundamental Filetypes
ls -l symbol File Type- regular filed directoryl symbolic linkb block special filec character special
filep named pipes socket
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Checking Free Space
bull df - Reports disk space usagendash Reports total kilobytes kilobytes used kilobytes freeper file
systemndash -h and -H display sizes in easier to read units
bull du - Reports disk space usagendash Reports kilobytes used per directoryndash Includes subtotals for each subdirectory
bull -s option only reports single directory summary
ndash Also takes -h and -H options
bull Applications-gtSystem Tools-gtDisk Usage Analyzer or baobab - Reports disk space usage graphically
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Removable Media
Mounting means making a foreign filesystem look like part of the main tree
Before accessing media must be mounted Before removing media must be unmounted By default non-root users may only mountcertain devices (cd dvd floppy usb etc) Mountpoints are usually under media
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Mounting CDs and DVDs
Automatically mounted in GnomeKDE Otherwise must be manually mounted
ndash CDDVD Reader
mount mediacdromndash CDDVD Writer
bull mount mediacdrecorder
eject command unmounts and ejects the disk
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Mounting USB Media
bull Detected by the kernel as SCSI devicesndash devsdaX or devsdbX or similar
bull Automatically mounted in GnomeKDEndash Icon created in Computer windowndash Mounted under mediaDevice ID
bull Device ID is built into device by vendor
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Mounting Floppy Disks
bull Must be manually mounted and unmountedndash mount mediafloppyndash umount mediafloppy
bull DOS floppies can be accessed with mtoolsndash Mounts and unmounts device transparentlyndash Uses DOS naming conventions
bull mdir abull mcopy homefiletxt a
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Archiving Files and Compressing Archives
bull Archiving places many files into one target filendash Easier to back up store and transferndash tar - standard Linux archiving command
bull Archives are commonly compressedndash Algorithm applied that compresses filendash Uncompressing restores the original filendash tar natively supports compression using gzip and
gunzip or bzip2 and bunzip2
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Creating Listing and Extracting File Archives
bull Action arguments (one is required)ndash -c create an archivendash -t list an archivendash -x extract files from an archive
bull Typically requiredndash -f archivename name of file archive
bull Optional argumentsndash -z use gzip compressionndash -j use bzip2 compressionndash -v be verbose
Classification Confidential
Thank You
Classification Confidential
Thank You
